I'm in the short-threads category, myself. If I'm going to say something, I want to contribute, that is to say something that hasn't already been covered, and frankly, I'm to lazy to parse through more than three or four pages of commentary, so with the fifth page, I assume someone has already said what I would have added.
Oh, and I'll reply to those who have addressed my posts, regardless of thread length, but I won't generally comment on anything new.
And it's a personal pet peeve when others repeat a question I answered, or restate an assumption that I've already called as in dispute (unless they challenge my logic or basis). I've begun to assume that long threads will start reiterating, as new people come in but don't read the whole thing.
238U.